zh/searchurl/bml/content/comparecells.js

   1 /**
   2  * Try to color the cells of comparison tables based on their contents.
   3  *
   4  * @title Compare cells
   5  */
   6 (function comparecells() {
   7         /* Create a new IFRAME to get a "clean" Window object, so we can use its
   8          * console. Sometimes sites (e.g. Twitter) override console.log and even
   9          * the entire console object. "delete console.log" or "delete console"
  10          * does not always work, and messing with the prototype seemed more
  11          * brittle than this. */
  12         let console = (function () {
  13                 let iframe = document.getElementById('xxxJanConsole');
  14                 if (!iframe) {
  15                         iframe = document.createElementNS('http://www.w3.org/1999/xhtml', 'iframe');
  16                         iframe.id = 'xxxJanConsole';
  17                         iframe.style.display = 'none';
  18
  19                         (document.body || document.documentElement).appendChild(iframe);
  20                 }
  21
  22                 return iframe && iframe.contentWindow && iframe.contentWindow.console || {
  23                         log: function () {}
  24                 };
  25         })();
  26
  27         /**
  28          * Get the text content for the given element.
  29          */
  30         function getTextFromElement(element) {
  31                 /* TODO: take IMG@alt, BUTTON@value etc. into account */
  32                 return element.textContent.trim().toLowerCase();
  33         }
  34
  35         /**
  36          * Get a Uint8Array of the SHA-256 bytes for the given string.
  37          */
  38         async function getSha256Bytes(string) {
  39                 try {
  40                         if (
  41                                 typeof crypto === 'object' && typeof crypto.subtle === 'object' && typeof crypto.subtle.digest === 'function'
  42                                 && typeof Uint8Array === 'function'
  43                                 && typeof TextEncoder === 'function'
  44                         ) {
  45                                 return new Uint8Array(await crypto.subtle.digest('SHA-256', new TextEncoder('utf-8').encode(string)));
  46                         }
  47                 } catch (e) {
  48                         return null;
  49                 }
  50         }
  51
  52         async function getColorsForValue(value) {
  53                 /* Cache the calculated values. */
  54                 getColorsForValue.cellValuesToRgb = getColorsForValue.cellValuesToRgb || {};
  55
  56                 if (!getColorsForValue.cellValuesToRgb[value]) {
  57                         let normalizedValue = value.trim().toLowerCase();
  58                         let hash;
  59
  60                         let yesValues = [
  61                                 '✔',
  62                                 'yes',
  63                                 'ja',
  64                                 'oui',
  65                                 'si',
  66                                 'sí'
  67                         ];
  68
  69                         let noValues = [
  70                                 'x',
  71                                 'no',
  72                                 'nee',
  73                                 'neen',
  74                                 'nein',
  75                                 'non',
  76                                 'no'
  77                         ];
  78
  79                         if (yesValues.indexOf(normalizedValue) > -1) {
  80                                 /* Make "Yes" cells green. */
  81                                 getColorsForValue.cellValuesToRgb[value] = [ 150, 255, 32 ];
  82                         } else if (noValues.indexOf(normalizedValue) > -1) {
  83                                 /* Make "No" cells green. */
  84                                 getColorsForValue.cellValuesToRgb[value] = [ 238, 32, 32 ];
  85                         } else if ((shaBytes = await getSha256Bytes(normalizedValue))) {
  86                                 /* Give other cells a color based on their content’s SHA
  87                                  * hash to ensure “consistent random colors” every time. */
  88                                 getColorsForValue.cellValuesToRgb[value] = [
  89                                         shaBytes[0],
  90                                         shaBytes[1],
  91                                         shaBytes[2]
  92                                 ];
  93                         } else {
  94                                 /* If the SHA hash could not be calculated, just use random
  95                                  * values. These will change on every execution. */
  96                                 getColorsForValue.cellValuesToRgb[value] = [
  97                                         Math.random() * 255,
  98                                         Math.random() * 255,
  99                                         Math.random() * 255
 100                                 ];
 101                         }
 102                 }
 103
 104                 /* Calculate/approximate the lightness (tweaked from “RGB to HSL”) to
 105                  * determine whether black or white text is best suited. */
 106                 let isLight = 150 < (
 107                         getColorsForValue.cellValuesToRgb[value][0] * 0.299
 108                         + getColorsForValue.cellValuesToRgb[value][1] * 0.587
 109                         + getColorsForValue.cellValuesToRgb[value][2] * 0.114
 110                 );
 111
 112                 return {
 113                         backgroundColor: 'rgb(' + getColorsForValue.cellValuesToRgb[value].join(', ') + ')',
 114                         color: isLight
 115                                 ? 'black'
 116                                 : 'white',
 117                         textShadow: isLight
 118                                 ? '1px 1px 3px white'
 119                                 : '1px 1px 3px black'
 120                 };
 121         }
 122
 123         /* The main function. */
 124         (function execute(document) {
 125                 Array.from(document.querySelectorAll('table')).forEach(table => {
 126                         Array.from(table.tBodies).forEach(tBody => {
 127                                 if (tBody.rows.length < 3) {
 128                                         console.log('Compare cells: skipping table body ', tBody, ' because it only has ', tBody.rows.length, ' rows');
 129                                         return;
 130                                 }
 131
 132                                 Array.from(tBody.rows).forEach(tr => {
 133                                         /* Determine the values. */
 134                                         let cellValues = [];
 135                                         let uniqueCellValues = new Set();
 136
 137                                         Array.from(tr.cells).forEach((cell, i) => {
 138                                                 /* Don't take the header cells into account. */
 139                                                 if (cell.tagName.toUpperCase() === 'TH') {
 140                                                         return;
 141                                                 }
 142
 143                                                 /* Assume the first cell is a header cell, even if it is not a TH. */
 144                                                 if (i === 0) {
 145                                                         return;
 146                                                 }
 147
 148                                                 cellValues[i] = getTextFromElement(cell);
 149                                                 uniqueCellValues.add(cellValues[i]);
 150                                         });
 151
 152                                         /* Color (or not) the cells based on the values. */
 153                                         let isFirstValue = true;
 154                                         let firstValue;
 155                                         cellValues.forEach(async function(cellValue, i) {
 156                                                 let hasTwoUniqueValues = uniqueCellValues.size == 2;
 157                                                 if (isFirstValue) {
 158                                                         firstValue = cellValue;
 159                                                         isFirstValue = false;
 160                                                 }
 161
 162                                                 let backgroundColor;
 163                                                 let color;
 164                                                 let textShadow;
 165
 166                                                 if (
 167                                                         uniqueCellValues.size == 1 ||
 168                                                         (hasTwoUniqueValues && cellValue === firstValue) ||
 169                                                         cellValue.trim() === ''
 170                                                 ) {
 171                                                         backgroundColor = 'inherit';
 172                                                         color = 'inherit';
 173                                                         textShadow = 'inherit';
 174                                                 } else {
 175                                                         backgroundColor = (await getColorsForValue(cellValue)).backgroundColor;
 176                                                         color = (await getColorsForValue(cellValue)).color;
 177                                                         textShadow = (await getColorsForValue(cellValue)).textShadow;
 178                                                 }
 179
 180                                                 tr.cells[i].style.setProperty('background-color', backgroundColor, 'important');
 181                                                 tr.cells[i].style.setProperty('color', color, 'important');
 182                                                 tr.cells[i].style.setProperty('text-shadow', textShadow, 'important');
 183                                         });
 184                                 });
 185                         });
 186                 });
 187
 188                 /* Recurse for frames and iframes. */
 189                 try {
 190                         Array.from(document.querySelectorAll('frame, iframe, object[type^="text/html"], object[type^="application/xhtml+xml"]')).forEach(function (elem) {
 191                                 execute(elem.contentDocument);
 192                         });
 193                 } catch (e) {
 194                         /* Catch exceptions for out-of-domain access, but do not do anything with them. */
 195                 }
 196         })(document);
 197 })();